Abstract

A novel protocol for ionic liquid (IL)-mediated C(sp )–H bond functionalization of 3,5-dimethyl-4-nitroisoxazoles 4 to substituted o-amino benzaldehydes 5 was developed in excellent yields. Isoxazolyl aryl ethanones 7 have been synthesized from isoxazolyl aryl ethanol synthon 6. Furthermore, utilizing the later as synthons for IL promoted Friedlander synthesis of highly functionalized isoxazole substituted quinoline libraries 9. The merit of this synthesis is easily available and eco- nomical starting materials, effective utilization of all the reactants, and simple workup procedure. It is noteworthy that ionic liquid used in C(sp )–H bond functionalization and Friedlander synthesis reactions can be recycled and reused five times without significant decrease in activity. Keywords Ionic liquid · C(sp )–H bond functionalization · Friedlander synthesis · Isoxazolyl quinolines Introduction their wide spectrum of biological activities [21]. One of the quinoline derivatives, Quinine (IV) shows antimalarial, It is well known that heterocyclic compounds play an impor- antipyretic, anti-inflammatory and analgesic properties. Qui- tant role in developing a new class of structural entities for noline based compound Mefloquine (V ) is known for potent pharmaceutical applications. Isoxazoles functionalized with anti-tubercular activity [22–25] have exhibited moderate to an additional nitrogen-containing group have had applica- sub micromolar anti-TB activity [26, 27]. Tibotec Medic-